1. Field of the Invention
The present invention relates to vehicle powertrain assemblies, and particularly to powertrain assemblies in which a transmission is incorporated within an engine crankcase. More particularly, the present invention relates to a powertrain assembly in which engine components are arranged in an improved configuration, which permits the engine to be made with a more compact width, and in which a modular transmission is easy to remove from, and replace in the engine crankcase for improved serviceability.
2. Description of the Background Art
In general, in a vehicle engine, the rotary speed of a crankshaft is changed to a predetermined slower speed by a clutch mechanism and a transmission, before power from the engine is transmitted to a driving wheel.
There is a known engine type which incorporates a transmission inside of the engine crankcase (for example, refer to Japanese Published Patent Application 7-99086). In this type of engine, the primary driven gear of a clutch mechanism, and an engine oil pump are arranged substantially in side-by side relation so as to overlap with one another, as viewed from a side view of the engine (for example, refer to Japanese Published Patent JP-B 62-33050).
However, when the clutch mechanism and the transmission are arranged so as to be coaxial to each other when viewed from the side of the engine, if the primary driven gear of the clutch mechanism and the oil pump are arranged to overlap with each, when viewed from the side of the engine as described above, the width of the engine becomes large, and the number of possible mounting positions of the engine within the vehicle becomes small.
For an engine incorporating a transmission in a crankcase, a number of transmissions that are cartridge-type or modular are known and commercially available. A modular transmission is capable of being detached from the crankcase and removed from the engine as a unit, in order to improve serviceability of the transmission.
Although the cartridge-type or modular transmission has advantages, there is a need for an improved powertrain that uses incorporates a cartridge-type transmission in an engine crankcase, because the structure around the cartridge-type transmission affects its serviceability.